noun
reclaimed wood; recycled wooden materials
Refers to old wood or used wooden items that are reused, often in construction, renovation, or furniture making. Can include beams, flooring, and furnishings.
このカフェの内装には古材が使われている。
Reclaimed wood is used in the interior of this café.
古材を再利用してテーブルを作った。
I made a table using recycled wooden materials.
Compound of 古 (old) and 材 (material, lumber). The reading こざい follows standard on'yomi. The term is straightforward and modern, with no obscure historical derivation.